SOx removal equipment for reducing sulfur oxides from flue gas from a boiler, a cooler provided on a downstream side of the SOx removal equipment, for reducing the sulfur oxides that remain in the flue gas and decrease a gas temperature, CO2 recovery equipment including an absorber for bringing CO2 in the flue gas into contact with a CO2 absorption liquid to be reduced, and a regenerator for causing the CO2 absorption liquid to emit CO2 to recover CO2 and regenerate the CO2 absorption liquid, a heat exchanger which is provided on an inlet passage side of the electric dust collector, for decreasing a temperature of the flue gas are included, and a mist generation material in the flue gas is converted from a gas state to a mist state to cause particulates in the flue gas to arrest and reduce the mist generation material in the mist state.